1. Field of the Technology
The present application relates generally to mobile stations operating in a wireless communication network, and more particularly to methods and apparatus for providing slot reservations for slotted messages in wireless communication networks.
2. Description of the Related Art
A wireless communication device, such as a mobile station operating in a cellular telecommunications network, may provide for both voice telephony and data communications. A mobile station may, for example, be compatible with 2nd Generation (2G) communication standards (such as Global System for Mobile Communications) or 3rd Generation (3G) communication standards (such as IS-2000 Release 0) and utilize Time Division Multiple Access (TDMA), or Code Division Multiple Access (CDMA) wireless access network technologies.
In CDMA communications defined by IS-2000, a mobile station operating in a normal slotted mode wakes up periodically and monitors its assigned paging channel slots for messages that are directed to the mobile station such as a Page Message. The mobile station monitors for mobile-directed messages in paging slots at an interval of 1.28*2^i seconds, where i is an integer value ranging from 0 to 7. The value of i is referred to as a “Slot Cycle Index” and is chosen by the mobile station and registered with the infrastructure. Slotted messaging has been utilized in wireless communication networks for many years in an effort to conserve battery power in mobile stations.
In Release D of IS-2000, a new feature that allows mobile stations to operate in a “reduced slotted mode” while idling and monitoring for slotted messages has been defined. Specifically, values of −4 to −1 are allowed as possible values for the Slot Cycle Index i for the reduced slotted mode. This enables faster call setup times for mobile-terminated calls. A shortened slot cycle for faster call setup is highly desirable for certain applications, such as Push-To-Talk (PTT) communication applications. The reduced slotted mode may be negotiated between the mobile station and the infrastructure at the time of call release, for example. In this case, the agreed upon value of i for the reduced slotted mode is active for a period of time before the mobile station and the infrastructure revert to the prior value of i for the normal slotted mode. Furthermore, when the mobile station is idle a new value of i can be negotiated to be active for a period of time.
Another reason that a mobile station may request to operate in the reduced slotted mode is unrelated to the need for fast call setup or PTT communications. In particular, if a mobile station is operating with a relatively high capacity or large power source (e.g. a wall power source, an automobile power source, or a PC power source through USB connection), it may request a shortened slot cycle as power savings is not a concern. The mobile station requests the reduced slot cycle in order to benefit from reduced call setup times even when another feature that requires it (e.g. PTT communications) is not active.
In the normal slotted mode, the mobile station has a relatively large amount of time in between its assigned paging slots. During this time period, the mobile station is able to operate in a “sleep mode” or perform any other operation that would otherwise not be possible while monitoring for slotted messages. Such operations include searching for a Global Positioning System (GPS) signal, scanning other CDMA frequencies different from the current one, or scanning for other wireless networks such as 802.11 (e.g. WiFi), GSM/GPRS, or UMTS networks. In the reduced slotted mode, however, the mobile station no longer has adequate time to perform such operations. If the mobile station performs such an operation in the reduced slotted mode, it may miss an assigned paging slot. If the infrastructure happens to send a message to the mobile station during this paging slot, the mobile station will miss the message. If the message is for setting up a call, then this may create a significant delay in call setup. It is for this reason that conventional mobile stations cannot suitably operate in this fashion while in the reduced slotted mode.
Other communication technologies may exhibit similar problems. Accordingly, what are needed are improved techniques for slotted messaging in wireless communication networks.